Domestic appliance



Sept. 6, 1955 M- E. FRY

DOMESTIC APPLIANCE Filed Dec. 4, 1953 INVEN TOR. Mil/0rd E. Fr y United States Patent DOMESTIC APPLIANCE Millard E. Fry, Dayton, 0h io, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application December4, 1953, Serial No. 396,209

2'Claims. (Cl. 200-140) This invention relates to a domestic appliance and more particularly to liquid actuated thermostats for domestic ovens and other similar applications.

For oven thermostats, it is customary to use the thermal expansion of a liquid in a control bulb to operate a switch or a valve or other control device. Unless the bulb is made very large, the expansion of the liquid is small for a rise of or 20 F.

it is an object of my invention to provide an arrangement in which the expansion of the liquid is enhanced.

it is another object of my invention to provide a, thermostatic bulb which will enhance the effect of the expansion of the thermal liquid in the bulb.

It is another object of my invention to provide a means which will automatically decrease the size of the bulb as the temperature increases.

These objects are attained in the form shown by providing two circular bimetal members arranged with their high expanding sides turned toward each other and bonded together at their edges. They are separated from one another from the areas within the bonded edges so as to provide an enclosure for a thermostatic liquid. The interior of this enclosure is connected by a suitable tube to a fluid motor which operates a switch or valve or other control device. In a modified form, only one of the walls is made of bimetal.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of the invention is clearly shown.

in the drawing:

Figure l is a diagrammatic representation of an electric oven provided with a thermostatic control embodying one form of my invention; and

Figure 2 is an enlarged view of one form of thermostat bulb embodying my invention.

Referring now to the drawing, there is illustrated an electric oven 20 containing an electric oven heating unit 22. This electric oven heating unit 22 is supplied with electric energy from the supply conductors 24 and 26. A switch 28 is connected between the supply conductors 26 and the conductor 30 connecting to the opposite end of the electric oven heating unit 22. The switch 28 is operated to the open position by a fluid motor 32 in the form of a wafer-shaped diaphragm. This diaphragm may be made of two circular disks having their edges bonded together and their remaining portions separated. This diaphragm through the lever 34 engages the operating pin of the switch 28 to open the switch 28. The light spring 36 holds the lever 34 in contact with the follower of the fluid motor 32. The interior of the fluid motor 32 is connected by a metal tube 38 with the interior of a thermostatic bulb 40. The interior of the thermostatic bulb 40 as well as the interior of the tube 38 and the diaphragm 32 is completely filled with a liquid suitable for thermal expansion such as chlorinated diphenyl. Other suitable liquids are mercury and a non-volatile oil.

2,717,291 Patented Sept. 6, 1955 It is normally-desired to cause the opening of the thermostat or valve by a rise of 10 or 20 F. This is diflicult because the expansion of such a liquid over such a range of temperatures is very small. According to my invention to enhance the thermal expansion of such a liquid I provide an arrangement whereby the size of the control bulb 40 decreases as the temperature rises so that its collapsing effect is added to the efiect of the expansion of the liquid within the bulb 40. Due to this, I make the bulb 40 out of two separate bimetal disks 42 and 44; The disks 42 and 44 may be shaped like a pie panand turned oppositely to provide a relatively large space between them. Their outer edges arebonded together to form a complete enclosure. The two bimetal disks 42 and 44 have their high expansion sides turned toward each other so that near rise in temperature will cause the disks 42 and 44 to bow toward each other and reduce the volume of the enclosure constituting the bulb 40. This will enhance the thermal expansion of the liquid Within the bulb 40 causing an added amount of the liquid to be transmitted through the tube 38 to the fluid motor 32. The amount of liquid supplied to the fluid motor 32 is the sum of the thermal expansion of the liquid in the bulb 40 plus the amount of contraction of the volume of the bulb 40 due to the bimetal wall members 42 and 44. The greatest effect is obtained when both sides of the bulb 40 are made of the bimetal material as explained before. However, the device is operative under many other different conditions. If desired, one of the bimetal diaphragms may be omitted and a disk of a single homogeneous material may be substituted as shown in Fig. 2. The bulb 40 may be provided with circular corrugations similar to the form of bulb shown in Fig. 2 to increase its flexibility.

In Figure 2, there is shown a practical form of bulb which includes a single corrugated bimetal diaphragm. This bulb designated by the reference character 14% includes a cup-shaped element of a single homogeneous metal. Set within this cup-shaped element 142 is a bimetal element 144 having an outer flange bonded to the cylindrical wall of the cup-shaped member 142. The central portion of this bimetal member 144 is pierced and provided with a flanged connector 146 which connects to the capillary tube 38 which may be identical to that shown in Figure 1. The connector 146 is bonded both to the tube 38 and to the bimetal 144 so as to provide a sealed connection. The bimetal member 144 is preferably provided with one or more circular corrugations as illustrated. The high expanding side of the bimetal is turned toward the interior of the bulb so that upon an increase in temperature the volume in the bulb 140 will decrease in a manner similar to the bulb 40.

In accordance with the provisions of Rule 78a, referonce is made to the following prior fiied application, Serial No. 354,953, filed May 14, 1953, now Pat. No. 2,678,379.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. A control including a fluid motor, a control device operatively connected to and operated by said fluid motor, a control bulb comprising an enclosure having a bimetal Wall portion adapted to deflect inwardly upon increases in its temperature to reduce the interior volume of the enclosure, a small conduit means connecting the interior of said control bulb with the interior of said fluid motor, and a liquid which expands and contracts uniformly at a relatively large rate with changes in temperature completely filling said fluid motor and said control bulb and said conduit means, the expansion of said liquid in said bulb and the reduction in volume of the bulb both causing movement of the liquid from the bulb to the fluid motor.

2. A control including a fluid motor, a control device operatively connected to and operated by said fluid motor, a control bulb comprising an enclosure having a bimetal wall portion adapted to deflect inwardly upon increases in its temperature to reduce the interior volume of the enclosure, a small conduit means connecting the interior of said control bulb with the interior of said fluid motor, and a liquid which expands and contracts uniformly at a relatively large rate with changes in temperature completely filling said fluid motor and said control bulb and said conduit means, said control bulb being formed of two members of bimetal material bonded together adjacent their edges and separated within the bonded portions to form the enclosure, said bimetal members being arranged with their high expanding sides facing inwardly, the expansion of said liquid in said bulb and the reduction in volume of the bulb both causing movement of the liquid from the bulb to the fluid motor.

References Cited in the file of this patent UNITED STATES PATENTS 

